The present invention relates generally to the field of solenoid valves and, more particularly, to an improved position sensor for a latching solenoid valve.
A variety of mechanisms have been used in the past to sense the position of a solenoid valve. Solenoid operated two-position latching valves are held in either open or closed positions by permanent magnetic flux and only require momentary energization of the solenoid coil to change the latched state. In many applications of such valves, it is desirable to have a continuous indication of the position of the valve.
Such position sensors have usually taken the form of a position indicator or switch which is coupled to the moving element of the valve, often through a seal or bellows. Alternately, and less commonly, a flux measuring sensor may be used to detect the flux mode operating on the valve, and thus the position of the valve. One such arrangement is shown in U.S. Pat. No. 5,394,131 (Langu). FIG. 7 of Langu discloses a magnetic drive with a primary armature and a secondary armature mounted on opposite sides of a solenoid coil. Both armatures are permanent magnets and the flux circuit is arranged such that there are two alternate flux paths, depending on the position of the primary armature. Motion of the secondary magnetized armature may be implemented by the mechanical displacement of the primary armature and resulting change in flux pattern from one path to the other. However, Langu is limited in that it teaches a symmetric circuit in which the indicating armature is sensitive to flux in both flux paths.
Hence, it would be beneficial to have a more versatile configuration in which the indicating armature need only be located in one flux path.
With parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiment, merely for the purposes of illustration and not by way of limitation, the present invention provides an improved solenoid (15) having a permanent magnet (16), a coil (18) adapted to be selectively energized by either a positive or negative current, a first pole-piece (19) and a second pole-piece (20), a first armature (21) positioned between the pole pieces, a first air-gap (22) and a second air-gap (23) between the armature and the first and second pole pieces, respectively, and a first magnetic flux path (24) and second magnetic flux path (25) associated with the first and second pole pieces, respectively, the armature being movable between an alternate first position (26) and second position (28) wherein flux from the magnet will hold the armature in either of the positions, the armature, magnet and air-gaps being so configured and arranged that selective energization of the coil produces a coil flux to cause the armature to move to and latch in one of the positions.
The improvement comprises the improved solenoid having an indicator pole piece (29), an indicator armature (30) being movable between a first indicator position (31) and a second indicator position (32), an indicator air-gap (33) between the indicator pole piece and the indicator armature, the indicator pole piece, armature, and air-gap being arranged in only one of the flux paths such that the magnet flux in the flux path influences the indicator armature, whereby the position of the indicator armature provides an indication of the position of the first armature.
The coil may be arranged to produce a coil flux in only one of the flux paths. The improved solenoid may also comprise at least one spring (35) arranged to bias the indicator armature toward the first indicator position. The first and second flux paths may conduct flux from only one permanent magnet.
The present invention also includes a solenoid wherein one of the air-gaps, and the corresponding pole piece and flux path are eliminated and instead are replaced with a spring and stop arranged to bias the first armature toward one of the armature positions.
Accordingly, the general object of the present invention is to provide an improved position sensor for a latching solenoid valve which properly indicates the position of the primary valve armature to show when the valve is in an open position and when it is in a closed position.
Another object is to provide an improved position sensor for a latching solenoid valve which indicates the position of the valve armature based on the orientation of the flux.
Another object is to provide an improved position sensor which allows for more versatile design and incorporation into the valve body.
Another object is to provide an improved position sensor in which the indicating armature is located in only one flux path.
Another object is to provide an improved position sensor which allows for the use of a variety of different valve armature compositions and configurations.
Another object is to provide an improved position sensor for a latching solenoid valve which allows for flexibility in latching strength.
Another object is to provide an improved position sensor which needs only a single magnet in the latching solenoid valve and position sensor.
Another object is to provide an improved position sensor for a latching solenoid valve which indicates the position of the valve through a microswitch.
These and other objects and advances will become apparent from the foregoing and ongoing written specification, the drawings, and the appended claims.